Library for storing data-storage media and having a removable interface module

ABSTRACT

A library for storing a cartridge of data-storage media includes a removable module and a chassis having a module receptacle. Cartridge storage slots are disposed within the chassis, and a media drive is disposed within the removable module. A cartridge transporter is disposed within the chassis and transports the cartridge between one of the cartridge slots and the media drive when the module is inserted within the module receptacle. A library control circuit is disposed within the chassis and controls the cartridge transporter. An interface circuit is disposed within the removable module and electronically interfaces a host computer to the media drive, and, when the removable module is inserted within the module receptacle of the chassis, electronically interfaces the host computer to the library control circuit.

TECHNICAL FIELD

[0001] The invention relates generally to electromechanical devices, andmore specifically to a library for storing cartridges of data-storagemedia, such as magnetic tape, and for providing read/write access to thestored media.

BACKGROUND OF THE INVENTION

[0002] Because today's computer users often store large volumes ofinformation on computer systems, it has become increasingly moreimportant to backup this information to non-volatile storage media, suchas magnetic tape or CD-ROM (Compact-Disc Read-Only Memory), and toarchive this media so that the stored information can be easilyretrieved. Furthermore, as the amount of a user's backed-up dataincreases, he often archives the storage media with the aid of acomputer to reduce inventory errors or other errors that may occur whenthe storage media are manually archived.

[0003] One type of device that is often used to archive data-storagemedia is a data storage library. Typically, the library is interfaced toa host computer system, and includes a media drive for reading data fromand writing data to the storage media, a section for archiving thestorage media, a section where an operator can load and unload thestorage media, and a mechanism for transporting the storage media amongthe load/unload section, the archive section, and the drive. Bycommunicating with or controlling the library, the host computer systemcan keep track of the specific information stored on a particularstorage medium and where in the library the particular storage medium islocated. Thus, when one wishes to retrieve specific archivedinformation, the host computer can control the transport mechanism toretrieve the storage medium containing the specific information and toinsert the storage medium into the media drive so that the computer canaccess the information.

[0004] A problem with such data storage libraries is that the on-boardtransport mechanism often requires a relatively large operating space,and thus significantly reduces the amount of space available for mediastorage.

[0005] Furthermore, in today's highly computerized environment, thereare many interface protocols and formats, including SCSI, fiber-channel,and ultra-wide interfaces. Therefore, a manufacturer often must makecostly and complex modifications to a library so that it can properlyinterface with a customer's computer system. Alternatively, themanufacturer can produce different versions of the library, one versionfor each interface protocol and format. But this also significantlyincreases overall manufacturing costs.

[0006] Additionally, many computer users want a storage library to berack-mountable so that it can be used to archive information from anentire computer network. But many libraries cannot be rack mountedbecause they are not properly sized to fit within the standard rackspace or because parts of the library, such as an open door, willencroach on the rack space occupied by a component mounted next to thelibrary. Furthermore, many of the libraries that are rack-mountable usethe allotted rack space inefficiently. For example, such libraries mayutilize the full width of the rack space but not the full depth.Moreover, many users want the storage library to be mountable within afraction of a standard rack width but to still have a relatively largeinformation storage capacity.

SUMMARY OF THE INVENTION

[0007] In one aspect of the invention, a library is provided for storinga cartridge of data-storage media. The library includes a removablemodule and a chassis having a module receptacle. Cartridge storage slotsare disposed within the chassis, and a media drive is disposed withinthe removable module. A cartridge transporter is disposed within thechassis and transports the cartridge between one of the cartridge slotsand the media drive when the module is inserted within the modulereceptacle. A library control circuit is disposed within the chassis andcontrols the cartridge transporter. An interface circuit is disposedwithin the removable module and electronically interfaces a hostcomputer to the media drive, and, when the removable module is insertedwithin the module receptacle of the chassis, electronically interfacesthe computer to the library control circuit.

[0008] Because the interface circuitry is mounted on a removable module,a library can be quickly and easily customized by inserting a modulethat provides the interface used by the customer's host computer orcomputer network. Furthermore, only one version of the base libraryunit, i.e., the chassis and the components mounted within the chassis,need be manufactured. This significantly reduces the cost and complexityof the manufacturing process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is an isometric view of a computer system including a hostcomputer coupled to a storage library that is in accordance with oneaspect of the invention.

[0010]FIG. 2 is an enlarged, exploded isometric view of portions of thestorage library of FIG. 1.

[0011]FIG. 3 is a block diagram of the circuitry of the storage libraryof FIG. 1.

[0012]FIG. 4 is an enlarged, isometric view of the cartridge transporterof the storage library of FIG. 1.

[0013] FIGS. 5A-5D show the respective positions of the cam mechanismand roller mechanism of the cartridge transporter of FIG. 4 during asequence where the transporter retrieves a cartridge from a storage slotand loads the cartridge into a media drive.

[0014]FIG. 6 is an enlarged, exploded isometric view of the latchmechanism of the storage library of FIG. 1.

[0015]FIG. 7 is an enlarged, isometric view of a digital-linear-tape(DLT) cartridge that can be stored by one embodiment of the storagelibrary of FIG. 1.

[0016]FIG. 8 is an enlarged, exploded isometric view of a door assemblyfor one embodiment of the storage library of FIG. 1.

[0017]FIG. 9 is a top view of the door assembly of FIG. 8.

[0018] FIGS. 10A-10C are cut-away top views of the door assembly ofFIGS. 8 and 9.

[0019]FIG. 11 is an isometric view of several storage libraries of FIG.1, that are rack mounted and that incorporate the door assembly of FIG.8.

DETAILED DESCRIPTION OF THE INVENTION

[0020] A computer system 10, which includes a conventional host computer12 and an embodiment of a data storage library 14 according to thepresent invention, is shown in FIG. 1. The library 14 communicates withthe computer 12 and allows the computer 12 to archive data to andretrieve data from one or more data storage media (such as shown in FIG.7) such as magnetic-tape cartridges or CD-ROMs. Under control of thecomputer 12, the library 14 receives data from the computer 12, recordsthe received data onto a storage medium, and then archives the storagemedium in a particular location within the library 14. To later accessthis data, the computer 12 instructs the library 14 to retrieve thestorage medium from the particular location, to read the data from themedium, and to route the read data back to the computer 12. If thecomputer system 10 is part of a larger computer network, then thecomputer 12 can be configured to allow other network components (notshown in FIG. 1), such as file servers or other computers, to archivedata to and retrieve data from the library 14. Furthermore, althoughshown coupled to the computer 12 in a desktop configuration, the library14 may be rack mounted and connected to a network component other thanthe computer 12.

[0021]FIG. 2 is an exploded isometric view of portions of the library 14of FIG. 1. The library 14 includes a chassis 16, which has a frontopening 18 and a rear receptacle 20. In one embodiment of the invention,the layout and construction of the components within the chassis 16allow the dimensions of the chassis 16 to be such that the library 14can be mounted in a conventional component rack (such as shown in FIG.9). For example, the chassis 16 may be approximately half a rack widthwide and substantially a full rack depth long. Furthermore, a doorassembly (such as shown in FIG. 8) may be mounted to the outside of thechassis 16 at the front opening 18.

[0022] A storage-media mailbox 22 is mounted adjacent to the frontopening 18 of the chassis 16 and includes a number of storage-mediumslots 24, which an operator can load and unload via the front opening18. Although the slots 24 can be constructed to hold any conventionaltype of a storage medium, for clarity they will be discussed hereinafteras cartridge slots 24, which can hold a conventional magnetic-tapecartridge (such as shown in FIG. 7). A latch mechanism 25 is mountedadjacent to a rear end of the mailbox 22 at the ends of the slots 24facing toward the rear receptacle 20. The latch mechanism 25 includesone latch 26 for each slot 24 to prevent the operator from inserting acartridge too far into a respective slot 24. Conventional optical sensorassemblies 28 are mounted along the sides of the mailbox 22, andgenerate respective optical beams across the slots 24. A broken beamindicates that a cartridge is currently within the respective slot 24.

[0023] Furthermore, in one embodiment, additional storage-medium slots30, which are not part of the mailbox 22, are mounted inside of thechassis 16 above the receptacle 20 and provide additional storagecapacity. Each of the slots 30 includes a respective roller 32, whichguides a cartridge as it is inserted into or removed from a slot 30.Conventional optical sensor assemblies 34, which are similar to thesensor assemblies 28, are mounted along the sides of the slots 30 withinthe chassis 16 to generate respective optical beams across the slots 30.A broken beam indicates that a cartridge is in a respective slot 30.

[0024] Each of the slots 24 of the mailbox 22 has an inner opening 38 atthe rear end of the mailbox, and a top-bottom sensor assembly 36generates a first optical beam across all of the inner openings 38 ofthe slots 24. Each of the slots 30 has an opening 40 located at an endfacing toward the mailbox 22, and the sensor assembly 36 also generatesa second optical beam across all of the openings 40 of the slots 30. Thesensor assembly 36 has the beams located such that a broken first beamindicates that a cartridge is sticking too far out from one of the slots24, and a broken second beam indicates that a cartridge is sticking toofar out from one of the slots 30. The sensor assembly 36 also includes atransporter vertical-position sensor assembly 42, which generates anoptical beam located such that the beam is broken when a storage-mediumtransporter is in a home position. The transporter is positioned withinthe chassis between the mailbox 22 and the slots 30, and is discussedbelow in conjunction with FIG. 4. The sensor assembly 36 also includes acam-position sensor-assembly 44, which generates an optical beam that isunbroken when a cam mechanism (such as shown in FIG. 4) of thestorage-medium transporter is in a home position.

[0025] A transporter drive assembly 46 moves the storage-mediumtransporter in a vertical direction so as to align the transporter witha selected one of the slots 24, the slots 30, or a conventional mediadrive 48, which is positioned in the rear receptacle 20 and is discussedbelow in greater detail. The drive assembly 46 includes a belt assembly50, which is driven by a transporter motor 52. In one embodiment, themotor 52 is a stepper motor, and a worm gear 54 is coupled to the shaftof the motor 52 and drives the belt assembly 50.

[0026] A roller drive assembly 55 drives a roller mechanism (such asshown in FIG. 4) of the storage-medium transporter. The roller driveassembly 55 includes a roller motor 56, which drives a roller driveshaft 58. In one embodiment, the motor 56 is a stepper motor and drivesthe shaft 58 via a worm gear (not visible in FIG. 2).

[0027] A cam drive assembly 60 drives the cam mechanism of thestorage-medium transporter. The cam drive assembly 60 includes a cammotor 62, which drives a cam drive shaft 64. In one embodiment, themotor 62 is a stepper motor and drives the shaft 64 via a worm gear 66.

[0028] A circuit board 68, which is shown in phantom line, is mounted tothe inside of the chassis 16 and includes a library control circuit thatcontrols the transporter drive assembly 46, the roller drive assembly 55and the cam drive assembly 60, monitors the condition of the sensorassemblies 28, 34, 36, 42, and 44, and otherwise controls the operationof the library 14 as discussed below in conjunction with FIG. 3.

[0029] A module 70 fits within the rear receptacle 20 of the chassis 16.The construction of the module 70 and the rear receptacle 20 allows theoperator to easily insert the module 70 into and remove the module 70from the rear receptacle 20. The module 70 includes the media drive 48and a circuit board 72, which includes an interface circuit (such asshown in FIG. 3) for interfacing the library control circuit on thecircuit board 68 with the computer 12 of FIG. 1. The media drive 48 andthe circuit board 72 are mounted to a sled 74, which, when inserted intothe rear receptacle 20, engages conventional left- and right-siderunners 76, which are mounted to the inside of the chassis 16. Aconnector 78 is mounted to the circuit board 72 and is coupled to theinterface circuit on the circuit board 72. The connector 78 mates with aconnector 80—which is mounted to the circuit board 68 and is coupled tothe library control circuit on the circuit board 68—when the module 70is fully inserted within the rear receptacle 20. Thus, the connectors 78and 80 provide a communication path between the library control circuitand the interface circuit. A connector 82, which is mounted to thecircuit board 72, provides a communication path between the interfacecircuit and the computer 12. Furthermore, when the module 70 is insertedwithin the rear receptacle 20, an opening 84 of the media drive 48,which receives the storage medium, is located below the slots 30 so thatthe storage-medium transporter can load and unload a storage medium intoand from the media drive 48 via the opening 84 without interference fromthe slots 30. Therefore, the top-bottom sensor assembly 36 is located toalso generate the second optical beam across the opening 84, so that acartridge sticking too far out of the opening 84 will break the secondbeam.

[0030] Because the module 70 is easily removable and insertable, theoperator or a technician can easily modify the library 14 at the factoryor in the field to meet a customer's specific requirements. For example,the operator or technician can modify the interface protocol and thetype of the drive 48 by merely inserting into the rear receptacle 20another module 70 having the appropriate media drive 48 and circuitboard 72. Different modules 70 can be provided for virtually all of theconventional interface protocols, including ultra-wide, fast SCSI,single-ended SCSI, differential SCSI, or fiber-channel.

[0031] Furthermore, the removable module 70 allows one to manufacture asingle version of the library 14 base unit, which includes all parts ofthe library 14 other than those included as part of the module 70. Thus,because only different versions of the module 70 need be manufactured tomeet a customer's specific interface and drive requirements, the costsand complexities of the manufacturing process are significantly lessthan for libraries that do not include such a removable module.

[0032] A power supply 86 and a power connector 88 are also mountedwithin the chassis 16. When connected to an external power source (notshown in FIG. 2) via the connector 88, the power supply 86 providespower to the circuit board 68, the drive assemblies 46, 55, and 60, andthe sensor assemblies 28, 34, 36, 42, and 44, and to the media drive 48and the circuit board 72 when the module 70 is installed within the rearreceptacle 20.

[0033]FIG. 3 is a schematic block diagram of the electronic circuitry ofthe library 14 of FIG. 2. But because the specific circuitry used withineach of the blocks is conventional, it is not discussed in detail.

[0034] This circuitry includes an interface circuit 90 and a media drivecircuit 92. The circuit 90 communicates with the computer 12 of FIG. 1via the connector 82 and is located on the circuit board 72, which, asdiscussed above in conjunction with FIG. 2, is located on the removablemodule 70. The media drive circuit 92 communicates with the interfacecircuit 90, and may be located entirely within the media drive 48 ofFIG. 2, entirely on the circuit board 72, or may have a portion that islocated within the media drive 48 and another portion that is located onthe circuit board 72.

[0035] A library control circuit 94 is located on the circuit board 68of FIG. 2 and communicates with the motors 52, 56, and 62, the sensorassemblies 28, 34, 36, 42 and 44, and the power supply 86 all of FIG. 2,and a keyboard display assembly 96, which allows the operator to inputdata or commands directly into the library 14 and to select differentsoftware options that the control circuit 94 supports. In oneembodiment, the library control circuit 94 includes one or moreconventional microprocessors or microcontrollers (not shown in FIG. 3).Furthermore, the connectors 78 and 80 allow power, control information,and data to be passed back and forth between the library control circuit94 and the interface circuit 90.

[0036] In one embodiment, the interface circuit 90 includes a hostinterface circuit 98 and a library interface circuit 100. The hostinterface circuit 98 is coupled to the computer 12 via the connector 82,and is also coupled to the library interface circuit 100, which iscoupled to the library control circuit 94. The media drive circuit 92 iscoupled t6 the host interface circuit 98, and in one embodiment is alsocoupled to the library interface circuit 100.

[0037]FIG. 4 is an isometric view of a storage-medium transporter 102,which is mounted in the chassis 16 of FIG. 2 between the mailbox 22 andthe slots 30 such that a front opening 104 of the transporter 102 facesthe mailbox 22 and a rear opening 106 faces the slots 30 and the rearreceptacle 20. In one embodiment, the transporter 102 moves verticallyup and down and is constructed to bi-directionally transport amagnetic-tape cartridge, such as a DLT cartridge (such as shown in FIG.7), through a passageway 107 extending between the front and rearopenings 104 and 106. Therefore, although the transporter 102 can beconstructed to transport any type of storage medium, for examplepurposes, the embodiment of the transporter 102 hereinafter describedwill be for transporting a DLT cartridge.

[0038] The transporter 102 includes spring-loaded front and rear rollerarms 108 and 110, which each pivot between an opened and closed positionto respectively release and grasp a cartridge. Each of the roller arms108 and 110 carries a respective portion of a roller mechanism 112,which includes a number of rollers 114. The rollers 114 are rotationallyintercoupled by meshing gears 116. The roller drive shaft 58 rotates aroller drive gear 118, which in turn drives the rollers 114 via thegears 116. The shaft 58 has a slot or keyway 120, which engages a splineor key along the inner circumference of the gear 118 to allow the gear118 to move freely up and down on the shaft 58 as the transporter 102moves up and down.

[0039] The transporter 102 is fixedly attached to the belt assembly 50by belt couplings 122. Furthermore, a support shaft 124 guides andstabilizes the transporter 102 as it is moved up and down along theshaft 124 by the belt assembly 50.

[0040] The transporter 102 also includes a cam mechanism 126, whichincludes a latch-release-and-front-roller-arm cam 128, afinal-push-and-rear-roller-arm cam 130, and cam intercoupling gears 132,134, and 136. The cam drive shaft 64 rotates a cam drive gear 138, whichin turn drives the cam mechanism 126. Like the roller drive shaft 58 andthe roller drive gear 118, the cam drive shaft 62 has a keyway and thecam drive gear 138 has a key such that the cam drive gear 138 can movefreely up and down on the cam drive shaft 62 as the transporter 102moves up and down. The cam gear 136 includes at least one homing opening140, which, when aligned with the optical beam generated by the camsensor assembly 44 of FIG. 2, indicates that the cam mechanism 126 is ina home position. Portions of the transporter 102 that are positionedbelow the gear 136 have openings that are aligned with the optical beamof the cam sensor assembly 44 such that when the opening 140 is in thehome position, the beam can pass through the opening 140 uninterrupted.

[0041] The transporter 102 also includes a latch-plunger assembly 142,which releases the latch mechanism 25 of FIG. 2 when the transporter 102is removing a cartridge from the mailbox 22. The transporter 102 alsoincludes a homing tab 144, which breaks the optical beam generated bythe vertical-position sensor assembly 42 of FIG. 2 when the transporter102 is in a home position.

[0042] Referring to FIGS. 2, 3, and 4, during operation of the library14, the operator inserts a cartridge into one of the slots 24 in themailbox 22 until the latch 26 of the slot stops the operator frominserting the cartridge any farther. Next, the transporter motor 52rotates and the transporter drive assembly 46 moves the transport 102upwards until the homing tab 144 breaks the beam generated by the sensorassembly 42. Then, the library control circuit 94 receives from therespective optical sensor assembly 28 a signal that indicates that thecartridge is within the slot 24. The circuit 94 next controls thetransporter motor 52 to rotate a known number of steps so that the driveassembly 46 moves the transporter 102 downward until the front opening104 of the transporter 102 is aligned with the slot 24 containing thecartridge. The counting of the steps may be conventional, or may takeinto account the backlash of the transporter drive assembly 46 asdiscussed below.

[0043] FIGS. 5A-5D show respective positions of the roller mechanism 112and the cam mechanism 126 during a load/unload sequence where thetransporter 102 retrieves a cartridge 146 from one of the storage slots24 of FIG. 2 and loads the cartridge into one of the slots 30 or themedia drive 48 of FIG. 2.

[0044] Referring to FIG. 5A, at some time before the transporter 102moves into its home position, the cam motor 62 rotates until the cammechanism 126 is in the home position. In this position, both of thefront and back roller arms 108 and 110 are in their respective openedpositions such that as the transporter 102 moves, the arms 108 and 110will not contact a cartridge 146 that is in one of the slots 24 or 30.As stated above, the circuit 94 of FIG. 3 determines that the cammechanism 126 is in the home position when the optical beam generated bythe sensor assembly 44 of FIG. 2 is unbroken. In one embodiment, thegear ratios of the cams 128 and 130 and the gears 132, 134, and 136 aresuch that the cam mechanism 126 is in the home position when either ofthe two openings 140 is aligned with the optical beam.

[0045] Still referring to FIG. 5A, it is known that in most gearsystems, such as the cam mechanism 126, there occurs a phenomenon knownas backlash. The degree of backlash is the amount of free play betweenthe gears as they rotate from one direction to another direction. Thatis, the manufacturing tolerances of the gear-tooth widths are often suchthat when the teeth of one gear are entered between the respective teethof a meshing gear, there are spaces between the adjacent gear teeth.Thus, before they engage, the gears must rotate slightly until one toothcontacts an adjacent tooth of a meshing gear. Therefore, because thenext position of the cam mechanism 126 is determined by counting thenumber of steps that the cam motor 62 of FIG. 2 rotates from the presentposition, the circuit 94 of FIG. 3 may be programmed to account for thebacklash when the rotational direction of the present rotation of thecam motor 62 is different than the rotational direction of theimmediately previous rotation.

[0046] In one embodiment, the circuit 94 accounts for backlash bystoring the number of rotational steps of the cam motor 62 needed tocompensate for the backlash. This number then becomes part of the totalnumber of steps required to rotate the cam motor 62 so that the cammechanism 126 will be in the desired position relative to the presentposition. The backlash number may be empirically determined, or may bedetermined for each cam mechanism 126 by rotating the cam mechanism 126in a first direction until the gears engage, rotating the cam mechanismin a second direction until the gears engage, and counting the number ofsteps that the cam motor 62 rotates in the second direction. Forexample, after the cam mechanism 126 is moved in a first direction intothe home position, the circuit 94 counts the number of steps—thebacklash number—that the cam motor 62 must rotate in the oppositedirection to move the cam mechanism 126 out of the home position. Asdiscussed above, this type of backlash compensation can also be used inthe transporter drive assembly 46. But backlash is typically much lessof a problem for a belt drive, and thus can often be ignored in abelt-driven assembly such as used for the transporter drive assembly 46.

[0047] Referring to FIG. 5B, once the transporter 102 has been alignedwith the appropriate slot 24 of FIG. 2, the cam motor 62 of FIG. 2rotates the appropriate number of steps such that the cam mechanism 126is in the mailbox-unload position. In this position, the cam 128 causesthe latch-plunger assembly 142 to disengage the latch 26 of the slot 24so that the transporter 102 can unload the cartridge 146 from the slot24. The cam 128 also causes the front roller arm 108 to close such thatthe rollers 114 of the roller mechanism 112 engage the side of thecartridge 146. The roller motor 56 of FIG. 2 then rotates apredetermined number of motor steps to rotate the rollers 114 such thatthey approximately center the cartridge 146 within the passageway 107 ofthe transporter 102. In one embodiment, the circuit 94 of FIG. 3compensates for backlash in the roller mechanism 112 as discussed abovefor the cam mechanism 126.

[0048] Still referring to FIG. 5B, the transporter motor 52 of FIG. 2rotates a predetermined number of motor steps to move the transporter102 up or down as needed to align the cartridge 146 within thetransporter 102 with its destination, which is either one of the slots30 or the opening 84 of the media drive 48, all of FIG. 2. The rearroller arm 110 remains open so that as the transporter 102 moves, theroller arm 110 does not contact another cartridge 146 that may be inanother one of the slots 30 other than the destination slot 30.

[0049] Referring to FIG. 5C, after the cartridge 146 has been alignedwith its destination, the cam motor 62 of FIG. 2 rotates a predeterminednumber of steps such that the cam mechanism 126 is in amedia-drive/rear-slot unload position. In this position, the cam 128disengages the latch-plunger assembly 142 and opens the front roller arm108. Furthermore, the cam 130 closes the rear roller arm 110. Once therear roller arm 110 is closed, the roller motor 56 of FIG. 2 rotates apredetermined number of steps such that the rollers 114 move thecartridge 146 into its destination.

[0050] If, as shown in FIG. 5C, the destination is one of the slots 30of FIG. 2, then the circuit 94 of FIG. 3 monitors the sensor assembly 36of FIG. 2 to determine if the second optical beam that is directedacross the openings 40 of the slots 30 and the opening 84 of the mediadrive 48 is broken or unbroken. If the beam is unbroken, then thecircuit 94 determines that the cartridge 146 has been fully insertedinto the destination slot 30. If the beam is broken, then the circuit 94causes the roller motor 56 to rotate additional steps until the rollers114 insert the cartridge 146 fully into the destination slot 30.Alternatively, instead of counting the number of steps that the rollermotor 56 rotates, the circuit 94 can cause the roller motor 56 tocontinue rotating until the beam is unbroken, thus indicating that thecartridge 146 has been fully inserted into the destination slot 30.

[0051] If, as shown in FIG. 5D, the cartridge destination is the mediadrive 48 of FIG. 2, then the rollers 114 often cannot fully insert thecartridge 146 into the opening 84 of the media drive 48. Thus, after theinitial moving of the cartridge into its destination as described inconjunction with FIG. 5C, the cartridge 146 is often inserted only partway into the opening 84. Therefore, the second optical beam is broken,and the circuit 94 of FIG. 3 controls the cam mechanism 126 to performan additional step called the “final push.” During this step, the cammechanism 126 pushes the cartridge 146 the remaining way into theopening 84, or at least far enough into the opening 84 so that theconventional cartridge intake mechanism of the media drive 48 isactivated. Once activated, the intake mechanism retracts the cartridge146 the remaining way into the media drive 48. More specifically, thetransporter drive assembly 46 moves the cartridge transporter 102 suchthat the cam 130 is aligned with the opening 84 of the media drive 48.The cam 130 rotates in the direction shown by the arrow in FIG. 5D so asto open the rear roller arm 110 and push the cartridge 146 into theopening 84. In one embodiment, this is the only step where therotational direction of the cam mechanism 126, specifically therotational direction of the cam 130, is not arbitrary, but is in theindicated direction so that a gradually sloped surface 145 of the cam130 engages the cartridge 146 and provides a relatively smooth pushthereto. In another embodiment, the cam 130 is more symmetrically shapedsuch that it can rotate in either direction for the final push.

[0052] Although FIGS. 5A-5D describe a sequence of steps fortransporting a cartridge 146 from one of the slots 24 of FIG. 2 to oneof the slots 30 or the media drive 48, the sequence is reversed fortransporting the cartridge 146 from the slot 30 or the media drive 48 toa slot 24.

[0053]FIG. 6 is an exploded isometric view of the latch mechanism 25,which is supported by a support wall portion 147 of the mailbox 22 ofFIG. 2. The latch mechanism 25 includes a pivot pin 148, which extendsthrough an opening 150 formed in each of latches 26. A latch spring 152is positioned between the back side of each latch 26 and a respectivespring receptacle 154, which is located on a mailbox support and jambmember 156 of the mailbox 22. For clarity, only one spring 152 and onereceptacle 154 are shown in FIG. 6. The latches 26 are biased by thesprings 152 to extend through respective latch openings 158 in a sideportion 160 of the mailbox 22. The latches 26 are pivoted back so as notto extend through the respective latch openings 158 when thelatch-plunger assembly 142 of FIG. 4 engages them.

[0054] A conventional DLT cartridge 146, such as shown in FIGS. 5A-5D,is shown in FIG. 7 with portions shown in phantom line. Although oneembodiment of the library 14 is constructed to receive DLT cartridges,other embodiments of the library 14 can be constructed to receive othertypes of storage media such as 4 millimeter (mm) and 8 mm tapecartridges. In such embodiments, the mailbox 22 and the slots 30 of FIG.2 are constructed to respectively receive such other media cartridges,and the respective removable module 70 of FIG. 2 includes a media drive48 for accepting such cartridges.

[0055]FIG. 8 is an exploded isometric view of one embodiment of thekeyboard/display panel 96 of FIG. 3 and one embodiment of a doorassembly 162 for the library 14 of FIG. 1. The keyboard/display panel 96includes a conventional display 164 and conventional punch keys 166, andallows the operator to manually input data and instructions to thelibrary control circuit 94 of FIG. 3. The library control circuit 94 mayalso display a software menu from which the operator can select functionoptions with the keys 166.

[0056] The door assembly 162 includes a door 168 having hinge cylinders170 and a cartridge-alignment protrusion 172, which engages thecartridge or cartridges 146 of FIG. 7 and ensures that they are fullyinserted into the slots 24 when the door 168 is closed. The door 168 mayalso include a lock 174, which impedes unauthorized access to themailbox 22 and any cartridges 146 therein. The lock 174 may be aconventional key lock, or may be an electronic lock that is controlledby the computer 12 of FIG. 1 via the library control circuit 94 of FIG.3.

[0057] The door assembly 162 also includes a hinge assembly 176, whichincludes a support plate 178, resilient extensions or fingers 180, andhinge cylinders 182. The support plate 178 is attached to aforward-facing front jamb portion 157 of mailbox jamb member 156, andthe hinge cylinders 170 of the door 168 are pivotally connected to thehinge cylinders 182. The hinge cylinders 170 and 182 are retained in aninterlocked position by a hinge pin 184 extending therethrough. Thefingers 180 extend out from an edge of the support plate 178 and curvetowards the front side of the support plate 178. The hinge cylinders 182are attached between the ends of adjacent ones of the fingers 180. Inone embodiment, resulting spaces 183 are defined between adjacent onesof the fingers 180. The spaces 183 are shaped to allow the operator toposition a finger therein so that the hinge assembly 176 does not hinderthe operator when grasping the cartridge 146 to insert or remove thecartridge 146 from one of the slots 24. Furthermore, the fingers 180 arerelatively rigid and resist movement in a vertical direction to providesolid support for the weight of the door 168.

[0058]FIG. 9 is a top view of the door assembly 162, and shows variouspositions of the door 168 as it moves between opened and closedpositions. Referring to FIGS. 8 and 9, the hinge cylinders 170 and 182of the door assembly 162, and the hinge pin 184 which extendstherethrough, are offset laterally inward from the sidewall 188 of thelibrary chassis 16 so that the door 168 can be opened withoutencroaching on an adjacent rack space. Specifically, a hinged side 186of the door 168 is positioned at or inward from the sidewall 188 of thelibrary chassis 16 when the door is closed. Thus, when the door 168 isin the closed position, it covers virtually the entire front side of thelibrary 14, including the hinge assembly 176, without encroaching on thespace occupied by any adjacent rack-mounted components, such as anotherlibrary 14. Furthermore, as the door 168 is opened or closed, the hingeassembly 176, as discussed below, prevents the hinged side 186 of thedoor 168 from encroaching on the adjacent rack space by reducing thedistance that the hinged side 186 extends beyond the sidewall 188 ascompared with conventional hinges. In one embodiment, no part of thehinged side 186 extends beyond the sidewall 188 when the door 168 isopened, closed, or in any position therebetween.

[0059] FIGS. 10A-10C are cut-away top views of the door assembly 162 andthe hinge assembly 176 when the door 168 is in a closed position,intermediate position, and opened position, respectively. Referring toFIG. 10A, the fingers 180 project forward from the support plate 178 andcurve laterally outward to position the hinge cylinders 182 spaced apartfrom the support plate 178 and to define a laterally open space 185therebetween. Referring to FIG. 10B, as the door 168 is rotated into theopened position, the hinged side 186 of the door 168 moves into thespace 185 so that the door 168 may be opened and closed uninhibited bythe offset hinge-line arrangement used. Specifically, fingers 180 areflexible in the outward (away from the chassis 16) and inward (towardthe chassis 16) directions such that as the hinged side 186 engages thefront of the plate 178, the fingers 180 flex to allow the hinged side186 to slide against the plate 178 as the door 168 moves between closedand opened positions. Furthermore, in one embodiment, the spring forcewith which the fingers 180 push the hinged side 186 against the plate178 is sufficient for the door 168 to be stable in many partially openpositions. Referring to FIG. 10C, when the door 168 is fully open, thefingers 180 return to their unflexed positions (as in FIG. 10A), and thehinged side 186 is parallel or approximately parallel to and abuts theplate 178. Because moving the door 168 toward the closed position causesthe fingers 180 to flex outward and force the side 186 against the plate178, the hinge assembly 176 tends to hold the door 168 open againstunintentional closing.

[0060] Referring to FIGS. 9 and 10C, in some embodiments, depending onthe angle the side 186 makes with a door front face 190, the door 168may open more than 90° such that portions of the front face 190 mayextend beyond the chassis sidewall 188. But this typically does notcause the door 168 to significantly encroach upon an adjacent space,because an adjacent component typically does not extend forward farenough for these encroaching portions of the front face 190 to contactthe adjacent component. But even if it is possible to open the door 168far enough to encroach, the door 168 need not open to more than anapproximately 90° position—which is not encroaching—to allow theoperator to insert and remove a cartridge 146 from the mailbox 22.

[0061] Referring to FIGS. 8 and 10B, in one embodiment, the fingers 180are, formed from a conventional plastic. But it has also been found thatwith repeated openings and closings of the door 168, the fingers 180 maybecome deformed from their desired shape. That is, the resiliency of thefingers 180 may be too low, and thus the hysteresis of the fingers 180may be too high, for the fingers 180 to maintain their desired shape.Therefore, a metal spring member 192 overlaying the fingers 180 is usedto increase the effective resiliency of the fingers 180. The springmember 192 includes a plate 194 that is installed between the jambportion 157 of the mailbox member 156 and the hinge plate 178. Thespring member 194 also includes fingers 196, which extend around andoverlay the fingers 180. The spring member 194 is formed from amaterial, such as metal, that has a significantly higher resiliency thanthe material from which the fingers 180 are formed. Thus, the fingers196 of the spring member 194 force the respective fingers 180 back intotheir desired shapes after each opening and closing of the door 168. Anactual door assembly 162 in accordance with this embodiment has beentested over a million times, and has been found to be very reliable.

[0062] Furthermore, referring to FIGS. 8, 9, and 10 c, it is noted thatwith the described door assembly 162, if the door 168 is pressed openfarther than the intended fully open position, the opening force appliedto move it beyond the fully open position will be resisted by the springforce of the fingers 180, and if present, the spring member 192. Thus,the fingers 180 and 196 can bend under this excess opening force withoutthe hinge assembly 176 breaking.

[0063]FIG. 11 is an isometric view of ten of the libraries 14—of FIG. 1mounted in a rack 200. As shown, neither the opened nor closed doors 168of the libraries 14 encroach on the respective rack spaces occupied bythe adjacent libraries 14.

[0064] From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A library for storing a cartridge of data-storage media, comprising:a removable module; a chassis having a module receptacle sized toreceive the removable module; cartridge storage slots disposed withinthe chassis; a media drive disposed within the removable module andhaving a drive opening, the media drive operable to receive and ejectthe cartridge through the drive opening; a cartridge transporterdisposed within the chassis and operable to transport the cartridgebetween one of the cartridge slots and the media drive when the moduleis disposed within the module receptacle; a library control circuitdisposed within the chassis and coupled to the cartridge transporter;and an interface circuit disposed within the removable module andcoupled to the media drive, the interface circuit being operable tointerface with a host computer that is external to the chassis, andbeing coupled to the library control circuit when the removable moduleis disposed within the module receptacle.
 2. The library of claim 1wherein the interface circuit comprises: a library interface circuitcoupled to the library control circuit when the removable module isdisposed within the module receptacle; and a host interface circuitcoupled to the media drive and to the library interface circuit, andoperable to interface with the host computer.
 3. The library of claim 1wherein the interface circuit comprises: a library interface circuitcoupled to the library control circuit when the removable module isdisposed within the module receptacle and coupled to the media drive;and a host interface circuit coupled, to the media drive and to thelibrary interface circuit, and operable to interface with the hostcomputer.
 4. The library of claim 1 wherein the library control circuitis operable to provide power to the media drive and to the interfacecircuit when the removable module is disposed within the modulereceptacle.
 5. The library of claim 1 wherein the interface circuit isoperable to couple data between the host computer and the media drivewhen the removable module is disposed within the module receptacle. 6.The library of claim 1 wherein the interface circuit is operable tocouple control information between the host computer and the librarycontrol circuit when the removable module is disposed within the modulereceptacle.
 7. The library of claim 1, further comprising a media-driveread-write-and-control circuit that is disposed within the removablemodule and that is coupled to the media drive and to the interfacecircuit.
 8. The library of claim 1 wherein the host computer comprises acomponent of a computer network.
 9. A library for storing a cartridge ofdata-storage media, comprising: a sled having a first signal connectorand a host signal connector; a chassis having a sled receptacle that isconstructed to allow insertion and removal of the sled therein, the sledreceptacle having a second signal connector that mates with the firstsignal connector when the sled is inserted into the sled receptacle;cartridge storage slots disposed within the chassis; a media drivemounted within the sled and having a cartridge receptacle; a cartridgetransporter assembly mounted within the chassis; a library controlcircuit mounted within the chassis and coupled to the cartridgetransporter assembly and to the second signal connector; and aninterface circuit mounted within the sled and coupled to the mediadrive, to the first signal connector, and to the host signal connector.10. The library of claim 9 wherein the interface circuit comprises: alibrary interface circuit coupled to the second signal connector; and ahost interface circuit coupled to the media drive, to the libraryinterface circuit, and to the host signal connector.
 11. The library ofclaim 9 wherein the interface circuit comprises: a library interfacecircuit coupled to the second signal connector and to the media drive;and a host interface circuit coupled to the media drive, to the libraryinterface circuit, and to the host signal connector.
 12. The library ofclaim 9 wherein: the chassis has a power connector that is coupled tothe library control circuit; the first signal connector has a power linecoupled to the interface circuit; and the second signal connector has apower line coupled to the library control circuit and coupled to thepower line of the first signal connector when the sled is inserted intothe sled receptacle such that power is provided from the library controlcircuit to the interface circuit and to the media drive when the sled isinserted into the sled receptacle.
 13. The library of claim 9 whereinthe host signal connector includes a data line such that the interfacecircuit allows data communication between the media drive and a hostcomputer.
 14. The library of claim 9 wherein the first, second, and hostsignal connectors each include a respective data line such that thefirst, second, and host signal connectors and the interface circuitallow communication of control information between the library controlcircuit and a host system computer when the sled is inserted into thesled receptacle.
 15. The library of claim 9, further comprising amedia-drive read-write-and-control circuit mounted within the sled andcoupled to the media drive and to the interface circuit.
 16. A methodfor providing a communication interface between a data-storage libraryand a host computer, the library having a library control circuit and amodule receptacle, the method comprising: coupling the library controlcircuit to an interface circuit by inserting into the module receptaclea module that includes the interface circuit and a media drive coupledto the interface circuit; and coupling the host computer to theinterface circuit.
 17. The method of claim 16, further comprisingactivating the interface circuit to allow communication between the hostcomputer and the media drive and between the host computer and thelibrary control circuit.
 18. The method of claim 16 wherein: theinterface circuit comprises a library interface circuit, and a hostinterface circuit coupled to the media drive and to the libraryinterface circuit; coupling the library control circuit comprisescoupling the library control circuit to the library interface circuit byinserting the module into the module receptacle; and coupling the hostcomputer comprises coupling the host computer to the host interfacecircuit.
 19. The method of claim 16 wherein the host computer comprisesa file server.
 20. A method for providing a communication interfacebetween a data-storage library and a host computer, the library having alibrary control circuit, a first signal connector coupled to the librarycontrol circuit, and a module receptacle, the method comprising:coupling the first signal connector to a second signal connector byinserting into the module receptacle a first module that includes thesecond signal connector, a third signal connector, a first media drive,and a first interface circuit coupled to the second and third signalconnectors and to the media drive; and coupling the host computer to thethird signal connector.
 21. The method of claim 20, further comprisingbefore the coupling the first signal connector: uncoupling a fourthsignal connector from the first signal connector by removing from themodule receptacle a second module that includes the fourth signalconnector, a fifth signal connector, a second media drive, and a secondinterface circuit different than the first interface circuit and coupledto the fourth and fifth signal connectors and to the second media drive;and uncoupling the host computer from the fifth signal connector. 22.The method of claim 20 wherein the interface circuit comprises: alibrary interface circuit coupled to the second connector; and a hostinterface circuit coupled to the media drive, to the third signalconnector, and to the library interface circuit.
 23. The method of claim20 wherein the host computer comprises a component of a computernetwork.